AAV gene therapy vectors in the TMJ.

OBJECTIVES: The goal of this project was to evaluate the use of two adeno-associated viral vector serotypes, adeno-associated viral vectors (AAV)-2 and AAV-6, approved for and used for gene therapy in humans, for the delivery of therapeutic genes to the temporomandibular joint (TMJ) and the attendant sensory nerves. METHODS: Young adult wild-type C57BL/6 mice were intra-articularly inoculated with AAV-2 and AAV-6 encoding the reporter gene gfp, the expression of which was assessed in the TMJ as well as along nerves innervating the TMJ. RESULTS: AAV-2 and AAV-6 serotypes were characterized by varying levels of tissue tropism demonstrating different efficacy of infection for articular chondrocytes, meniscal fibroblasts, and trigeminal neurons. Specifically, AAV-2 infected both neurons and articular chondrocytes/meniscal fibroblasts, whereas AAV-6 showed selectivity primarily for neurons. CONCLUSIONS: The results of this study are clinically significant in the successful application of gene therapy vectors for TMJ disorders, as this new knowledge will allow for appropriate targeting of specific therapeutic genes to selective tissues (neurons vs. chondrocytes/fibroblasts) as needed by using specific viral vector serotypes.

Conditional ablation of E-cadherin in the oral epithelium progeny results in tooth anomalies.

OBJECTIVES: The objective of this study is to confirm the developmental origin of the enamel organ and evaluate the role of E-cadherin in tooth development by conditional deletion in the oral epithelium and its enamel organ progeny. K5-Cre;ROSA26 compound mice were included in this study in order to confirm the oral epithelial origin of the enamel organ, as well as of the action of the K5-Cre transgene in ablating E-cadherin in the enamel organ. K5-Cre;Ecadfl/fl knockout mice were included to evaluate the effects of the conditional E-cadherin ablation onto tooth development. MATERIAL AND METHODS: K5-Cre transgenic mice were crossed into the ROSA26 reporter mouse to trace the cell fate of the oral epithelium and its progeny in vivo. Moreover, K5-Cre mice were crossed into the Ecadfl/fl mice to produce K5-Cre;Ecadfl/fl compound mouse, as well as K5-Cre;Ecadfl/+ and Ecadfl/fl littermate controls. These litters were euthanized at postnatal day P2 to study the effects of conditional E-cadherin ablation in vivo. RESULTS: The K5-Cre;ROSA26 compound mouse demonstrated that the origin of the enamel organ and the structures thereof are of oral epithelial origin. Furthermore, using the K5-Cre;Ecadfl/fl compound mouse, we determined that conditional ablation of E-cadherin in the oral epithelium, and its progeny, results in dental anomalies involving elongation of the molar root, shrinkage of the pulp space, and alterations of the periapical area, including cementum hyperplasia. The K5-Cre;Ecadfl/fl mice also displayed a smaller overall stature compared with heterozygotes and wild-type littermates. CONCLUSIONS: E-cadherin is important in tooth development, including the formation of enamel, the crown, pulp space, and the roots.

Calcitonin gene-related peptide: An intra-articular therapeutic target for TMJ disorders.

OBJECTIVES: The goal of this project was to evaluate the role of calcitonin gene-related peptide (CGRP) in the development of arthritis. METHODS: Herein, we employed somatic mosaic analysis in two different joints by FIV(CGRP) intra-articular inoculation in the knees or temporomandibular joints (TMJ) of young adult male C57/BL6 mice. FIV(CGRP) is a feline immunodeficiency virus over-expressing full-length CGRP. Joint pathology and function were evaluated at the histopathological and behavioral levels. In addition, CGRP signaling was inhibited by intra-articular inoculation using FIV(CGRP8-37 ), such that the inhibitory peptide CGRP(8-37) was overexpressed 4 weeks after induction of joint inflammation in the TMJ of IL-1ßXAT transgenic mouse model. The mice were evaluated for behavior and killed for evaluation of knee and TMJ pathology. RESULTS: Overexpression of CGRP in the joints of wild-type mice induced the development of joint anomalies, including meniscal hypertrophy and articular pathology, associated with nocifensive behavior. Intriguingly, overexpression of the CGRP(8-37) inhibitory peptide in the knee and TMJ of IL-1ßXAT transgenic mice with joint inflammation resulted in partial amelioration of the attendant joint pathology. CONCLUSIONS: The results of this study suggest that CGRP is sufficient and necessary for the development of joint pathology and may serve as an intra-articular therapeutic target using gene therapy or monoclonal antibody-based therapies.

Partial epithelial-mesenchymal transition during enamel development.

OBJECTIVES: We set out to investigate whether a hybrid stem-like p-EMT phenotype develops during murine molar enamel development in vivo. SETTING AND SAMPLE POPULATION: Histology specimens incorporating molar tooth buds harvested from mice at post-natal day 4 (P4) were included in our studies. MATERIALS AND METHODS: We employed double immunofluorescence staining to analyze the simultaneous expression of the epithelial marker E-cadherin and the mesenchymal marker N-cadherin in histology specimens with tooth buds harvested from P4 mice. Moreover, we evaluated the expression of the core master stem cell markers Oct4 and Sox2, as well as the mature ameloblast marker amelogenin. RESULTS: Here we document the co-expression of E-cadherin and N-cadherin in a sub-population of pre-ameloblasts in the inner enamel epithelium suggestive of the presence of a hybrid epithelial/mesenchymal phenotype resulting from p-EMT. Moreover, the core stem cell factors Oct4 and Sox2 colocalized with E-cadherin expressing pre-ameloblasts, whereas the mesenchymal marker N-cadherin was expressed specifically by amelogenin-positive mature secretory ameloblasts. CONCLUSIONS: The differentiation of E-cadherin-positive pre-ameloblasts towards N-cadherin-positive mature secretory ameloblasts transition through a previously unidentified epithelial/mesenchymal stage derived through p-EMT, co-expressing the master transcription factors Oct4 and Sox2.

Reprogramming oral epithelial keratinocytes into a pluripotent phenotype for tissue regeneration.

OBJECTIVES: We set out to reprogram adult somatic oral epithelial keratinocytes into pluripotent cells for regenerative dentistry. SETTING AND SAMPLE POPULATION: Immortalized murine oral keratinocyte cell (IMOK) line raised from adult mouse mucosa were cultured in vitro in our studies. MATERIALS AND METHODS: Adult murine oral epithelial keratinocytes were chronically treated with TGF-ß1 in vitro, and the expression of Oct4, Nanog, Sox2 and Nestin, as well as specific homeobox Gata and Pax gene family members were investigated. RESULTS: We documented the induction of stem factors linked with pluripotency and/or the maintenance and regulation of stem-cell self-renewal in oral epithelial keratinocytes by TGFß1. Moreover, we discovered that this TGF-ß1-induced increase in Oct4, Nanog, Sox2 and Nestin was inhibited by SB431542, suggesting that TGF-ß1 signals via the TGF-ßRI receptor to induce pluripotency and stemness. CONCLUSIONS: Adult oral epithelial keratinocytes treated chronically with TGF-ß1 acquired phenotypic characteristics consistent with pluripotent stem cells, highlighting the facileness of reprogramming adult oral keratinocytes into an unlimited supply of pluripotent stem cells.

Serotonin contributes to the in vitro production of a biomimetic enamel-like material from reprogrammed oral epithelial keratinocytes.

OBJECTIVES: To evaluate the role of serotonin in the development of a biomimetic enamel-like material in vitro. SETTING AND SAMPLE POPULATION: Immortalized murine oral keratinocytes raised from adult mouse mucosa were cultured in vitro. In addition, specimens incorporating molar tooth buds harvested from mice were included in our studies. MATERIALS AND METHODS: We used cell-based scaffold-free tissue engineering to assemble three-dimensional (3D) organoids into complex tissue constructs that closely emulate the complexity of adult enamel. We also analysed mouse molar specimens using immunohistochemistry for serotonin expression as well as its cognate receptor. RESULTS: TGF-ß1-reprogrammed murine oral keratinocytes formed organoids that laid down an amelogenin-rich protein matrix when grown as three-dimensional (3D) cultures in the presence of serotonin. Following mineralization, the newly formed crystals were densified under pressure and vacuum to produce a biomimetic enamel-like material that demonstrated parallel alignment of hydroxyapatite crystals with some interspaced residual organoid matter into enamel prism-like structures conferring size, mechanical properties comparable to tooth enamel, including light translucency. Serotonin expression was localized by immunohistochemistry proximal to the enamel organ of developing molar buds. Moreover, serotonin HTRb2 receptor expression was localized on ameloblasts within the enamel organ proximal to the area where serotonin was immunolocalized. CONCLUSIONS: Our results demonstrate that serotonin is inductive in the development of a biomimetic enamel-like material from reprogrammed oral epithelial keratinocytes in vitro. The facileness of harvesting adult somatic cells together with the versatility of our approach offers exciting opportunities to address regenerative challenges linked to lost enamel.

Effects of vascular endothelial growth factor on osteoblasts and osteoclasts.

INTRODUCTION: Bone remodeling is crucial to the success of many dental procedures and is tightly regulated. Vascular endothelial growth factor (VEGF), a key cytokine for angiogenesis, is also an important regulator of bone remodeling. We aimed to examine the mechanisms by which VEGF induces bone remodeling by studying its effects on cultured osteoblasts and osteoclasts. METHODS: Preosteoblastic MC3T3-E1 cells were treated with vehicle or VEGF-A165. Cell proliferation, migration, and invasion potentials were assessed. Preosteoclastic RAW264.7 cells were treated with vehicle or VEGF with or without the receptor activator of nuclear factor kappa-B ligand (RANKL), and osteoclast formation was measured with tartrate-resistant acid phosphatase staining. Conditioned media from vehicle-treated or VEGF-treated MC3T3-E1 cells were tested for the levels of RANKL and osteoprotegerin (OPG) and were used to treat RAW264.7 cells to observe osteoclast formation. RESULTS: VEGF significantly induced MC3T3-E1 cell proliferation, migration, and invasion. VEGF did not directly induce osteoclastogenesis but significantly increased the RANKL/OPG ratio in the conditioned media from the MC3T3-E1 cultures; this significantly increased osteoclast formation. CONCLUSIONS: VEGF stimulates osteoclast differentiation by increasing the osteoblastic RANKL/OPG ratio but has no direct effect on osteoclast precursor cells, and it induces osteoblast proliferation, migration, and invasion potentials in vitro.

Neurologic Regulation and Orthodontic Tooth Movement.

Pain and discomfort are prevalent symptoms among the vast majority of patients with fixed orthodontic appliances and is the most disliked aspect of treatment. The periodontium is a highly innervated structure that also provides the necessary trophic factors, such as nerve growth factor, which promote neuronal survival, maintenance and axonal growth, via interaction with specific nerve surface receptors, such as TrkA. Various types of nerves are found in the periodontium, including thinly myelinated and unmyelinated sensory fibers that express the neuropeptides substance P and calcitonin gene-related peptide among others. Tooth movement activates peripheral sensory nerve endings, which transmit painful signals to the brain after being processed at the trigeminal spinal nucleus, resulting in local expression of pain related genes, such as c-Fos. Concurrently, an attendant inflammatory process is detected in the trigeminal spinal nucleus, including activation of astrocytes, microglia and neurons. This complex neurologic reaction to tooth movement mediates orthodontic pain and also serves a source of neurogenic inflammation exhibited in the trigeminal spinal nucleus and the periodontium. Activated periodontal sensory fibers release neuropeptides in the periodontal environment, which in turn induce a local inflammatory cascade aiding in alveolar bone turnover and tooth movement per se. Control of pain with nonsteroidal anti-inflammatory drugs and other prescription or over-the-counter pain killers effectively reduce this neurologic reaction and alleviate the attendant pain, but also reduce the neurogenic inflammatory component of orthodontic tooth movement causing a slowdown in bone turnover and consequently delaying orthodontic treatment.

Differential modulation of methamphetamine-mediated behavioral sensitization by overexpression of Mu opioid receptors in nucleus accumbens and ventral tegmental area.

RATIONALE: Repeated administration of methamphetamine (Meth) induces behavioral sensitization which is characterized by a progressive increase in locomotor response after each injection. Previous studies have shown that Mu opioid receptors (MORs) can regulate Meth-mediated behavioral sensitization. However, the reported interactions are controversial; systemic activation of MORs either enhanced or suppressed Meth sensitization. It is possible that alteration of Meth sensitization after systemic administration of MOR ligands reflects the sum of distinct MOR reactions in multiple brain regions. OBJECTIVES: The purpose of the present study was to examine the actions of MORs on Meth sensitization after regionally selective overexpression of human MOR through an AAV6-based gene delivery system. METHOD: We demonstrated that adeno-associated virus (AAV)-MOR increased MOR immunoreactivity and binding in vitro. AAV-MOR or AAV-green fluorescent protein (GFP) was injected into the nucleus accumbens (NAc) or ventral tegmental area (VTA) of adult mice. Two weeks after viral infection, animals received Meth or saline for five consecutive days. Locomotor behavior and striatal dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) level were determined. RESULTS: Repeated administration of Meth progressively increased locomotor activity; this sensitization reaction was attenuated by intra-NAc AAV-MOR microinjections. Infusion of AAV-MOR to VTA enhanced Meth sensitization. AAV-MOR significantly enhanced DA levels in VTA after VTA infection but reduced DOPAC/DA turnover in the NAc after NAc injection. CONCLUSION: Our data suggest a differential modulation of Meth sensitization by overexpression of MOR in NAc and VTA. Regional manipulation of MOR expression through AAV may be a novel approach to control Meth abuse and psychomimetic activity.

Accelerated orthodontic tooth movement: molecular mechanisms.

Accelerating orthodontic tooth movement can significantly reduce treatment duration and risks of side effects. The rate of orthodontic tooth movement is chiefly determined by the remodeling of tissues surrounding the roots; this in turn is under the control of molecular mechanisms regulating cellular behaviors in the alveolar bone and periodontal ligament. This review summarizes the current knowledge on the molecular mechanisms underlying accelerated orthodontic tooth movement, and the clinical and experimental methods that accelerate orthodontic tooth movement with possible molecular mechanisms. The review also shows directions for future studies to develop more clinically applicable methods to accelerate orthodontic tooth movement.

Ectodomain-specific E-cadherin antibody suppresses skin SCC growth and reduces tumor grade: a multitargeted therapy modulating RTKs and the PTEN-p53-MDM2 axis.

Tumor cell survival consists of an intricate balance between cell growth and cell death pathways involving receptor tyrosine kinases [RTK; i.e., HER1-4, insulin-like growth factor-1 receptor (IGF-1R), etc.], MDM2, and the tumor suppressor proteins phosphatase and tensin homolog deleted on chromosome ten (PTEN) and p53. We recently demonstrated that shedded E-cadherin extracellular domain fragment (sEcad) is a valid oncogenic target that is significantly increased in human clinical skin squamous cell cancers (SCC) samples, UV-induced mouse tumors, and cells and promotes tumor cell proliferation, migration, and invasion by interacting and activating with the HER-phosphatidylinositol 3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase (MAPK) axis. In resected human SCC tumors, we reported enhanced sEcad-HER1, sEcad-HER2, and sEcad-IGF-1R, but not FL-Ecad-RTK interactions. Here, we demonstrate that a sEcad antibody against the ectodomain of E-cadherin suppressed SCC growth and increased tumor differentiation in orthotopic cutaneous SCC xenografts by inhibiting proliferation and inducing apoptosis. A similar anti-sEcad antibody-induced inhibition of proliferation and induction of cell death was evident in PAM212 cells in vitro. Mechanistically, anti-sEcad administration upregulated an array of cell death pathways (i.e., Bad, active caspase-3, and cleaved PARP) and inhibited inhibitors of apoptosis (IAP; survivin, livin, etc.), RTKs (HER1, HER2, p95HER2, and IGF-1R), MAPK and PI3K/mTOR prosurvival signaling. Interestingly, in anti-sEcad mAb-treated tumors and PAM212 cells, this effect was associated with a profound increase in membrane, cytosolic, and nuclear levels of PTEN; enhanced cytosolic p53; and a decrease in MDM2 levels. Overall, our studies suggest that an antibody-based therapy against sEcad may be a novel therapeutic platform for cutaneous SCCs by hampering key proto-oncogenes (RTKs, IAPs, and MDM2) and activating potent tumor suppressor proteins (PTEN and p53) intricately linked to tumor growth and survival.

Soluble-E-cadherin activates HER and IAP family members in HER2+ and TNBC human breast cancers.

Recent literature suggests that sEcad exerts pro-oncogenic effects, possibly acting as a ligand for the human epidermal growth factor family. Here we show that sEcad is a novel candidate protein for drug targeting since it is increased in human and mouse HER2-positive (HER2+) breast tumors, MMTV-PyMT bodily fluids and human cell culture systems. Mechanistically, we show that endogenous sEcad, and to a lesser extent membrane-bound E-cadherin, associates with HER1, HER2, and HER3 in human and MMTV-PyMT mouse HER2+ tumors and with HER1 in triple negative breast cancer (TNBC) specimens. Furthermore, addition of exogenous recombinant human E-cadherin/Fc chimeric protein (rhEcad/Fc; sEcad) to HER2+ MCF-7, SKBR3, and HER2-negative MDA-MB-231 TNBC cells, resulted in sEcad-HER receptor family interactions, activation of HER1-4 and downstream pro-survival signaling, including the MAPK-PI3K/Akt/mTOR pathways and IAP family members. Lastly, we demonstrate that sEcad exerts pro-oncogenic effects via HER signaling, and acts additively with the HER ligand EGF to promote HER2+ breast cancer proliferation and migration, as well as TNBC invasion. Because sEcad associates and activates many of the oncogenic pathways that tumors utilize for growth and survival and serum levels in patients correlates with clinical response, suggests that targeted therapy against sEcad in combination with other therapies may potentially offer a novel therapeutic strategy for the treatment of breast cancers.

Monoclonal antibody against the ectodomain of E-cadherin (DECMA-1) suppresses breast carcinogenesis: involvement of the HER/PI3K/Akt/mTOR and IAP pathways.

PURPOSE: Although targeted therapies against HER2 have been one of the most successful therapeutic strategies for breast cancer, patients eventually developed acquired resistance from compensatory upregulation of alternate HERs and mitogen-activated protein kinase-phosphoinositide 3-kinase (PI3K)/Akt/mTOR signaling. As we and others have shown that the soluble ectodomain fragment of E-cadherin exerts prooncogenic effects via HER1/2-mediated binding and activation of downstream prosurvival pathways, we explored whether targeting this ectodomain [DECMA-1 monoclonal antibody (mAb)] was effective in the treatment of HER2-positive (HER2(+)) breast cancers. EXPERIMENTAL DESIGN: MMTV-PyMT transgenic mice and HER2(+)/E-cadherin-positive MCF-7 and BT474 trastuzumab-resistant (TtzmR) cells were treated with the DECMA-1 mAb. Antitumor responses were assessed by bromodeoxyuridine incorporation, apoptosis, and necrosis. The underlying intracellular prooncogenic pathways were explored using subcellular fractionation, immunoprecipitation, fluorescence microscopy, and immunoblotting. RESULTS: Treatment with DECMA-1 mAb significantly delayed tumor onset and attenuated tumor burden in MMTV-PyMT mice by reducing tumor cell proliferation and inducing apoptosis without any detectable cytotoxicity to mice or end-organs. In vitro treatment of MCF-7 and BT474 TtzmR cells reduced proliferation and induced cancer cell apoptosis. Importantly, this inhibition of breast tumorigenesis was due to concomitant downregulation, via ubiquitin-mediated degradation through the lysosome and proteasome pathways, of all HER family members, components of downstream PI3K/Akt/mTOR prosurvival signaling and suppression of inhibitor of apoptosis proteins. CONCLUSIONS: Our results establish that the E-cadherin ectodomain-specific mAb DECMA-1 inhibits Ecad(+)/HER2(+) breast cancers by hindering tumor growth and inducing apoptosis via downregulation of key oncogenic pathways involved in trastuzumab resistance, thereby establishing a novel therapeutic platform for the treatment of HER2(+) breast cancers.

Sustained interleukin-1ß overexpression exacerbates tau pathology despite reduced amyloid burden in an Alzheimer's mouse model.

Neuroinflammation is an important component of Alzheimer's disease (AD) pathogenesis and has been implicated in neurodegeneration. Interleukin-1 (IL-1), a potent inflammatory cytokine in the CNS, is chronically upregulated in human AD and believed to serve as part of a vicious inflammatory cycle that drives AD pathology. To further understand the role of IL-1ß in AD pathogenesis, we used an inducible model of sustained IL-1ß overexpression (IL-1ß(XAT)) developed in our laboratory. The triple transgenic mouse model of AD, which develops plaques and tangles later in its life cycle, was bred with IL-1ß(XAT) mice, and effects of IL-1ß overexpression on AD pathology were assessed in F1 progeny. After 1 and 3 months of transgene expression, we found robust increases in tau phosphorylation despite an ∼70-80% reduction in amyloid load and fourfold to sixfold increase in plaque-associated microglia, as well as evidence of greater microglial activation at the site of inflammation. We also found evidence of increased p38 mitogen-activated protein kinase and glycogen synthase kinase-3ß activity, which are believed to contribute to tau phosphorylation. Thus, neuroinflammation regulates amyloid and tau pathology in opposing ways, suggesting that it provides a link between amyloid accumulation and changes in tau and raising concerns about the use of immunomodulatory therapies in AD.

Autosomal dominant mesomandibular fibro-osseous dysplasia: a self-resolving inherited fibro-osseous lesion of the jaws.

A hereditary congenital condition characterized by a fibro-osseous lesion sharing some features with fibrous dysplasia and affecting the middle aspect of the mandible is presented. The condition was initially described as congenital monostotic fibrous dysplasia in two siblings, a male and a female. However, there is sufficient evidence that the disorder is autosomal dominant since it has been encountered in two of four children, both males, of the female propositus and one child, a boy, of the male propositus. All patients presented at birth or right after birth with enlargement of the middle part of the mandible. Radiographs from affected individuals have shown mesomandibular enlargement with irregular trabeculation akin of "ground-glass" appearance. Histologically, samples from all patients revealed woven bone proliferation in a cellular fibroblastic stroma. Interestingly, the originally described siblings, now in their 30s, have no evidence of jaw lesions either radiographically or clinically, thus indicating that the condition is self-limiting or self-resolving. An autosomal dominant mode of inheritance with apparent male predilection is favored. The molecular basis of this condition is currently unknown. However, the location of the lesions in the middle aspect of the mandible suggests dysregulation of Bone Morphogenetic Protein (BMP) signaling since BMPs regulate mandibular morphogenesis in utero, particularly in the medial region as well as postnatal bone remodeling. Immunohistochemical evaluation for a BMP-binding protein Twisted Gastrulation (TWSG1) revealed mosaic pattern of staining, with some cells, including osteoclasts, strongly stained and others exhibiting faint or no staining, thus supporting active regulation of BMP signaling within the lesion. Future investigations will determine if dysregulation of BMP signaling plays a causative role or rather reflects secondary activation of repair mechanisms and/or bone remodeling.

Conditional expression of human ß-hexosaminidase in the neurons of Sandhoff disease rescues mice from neurodegeneration but not neuroinflammation.

This study evaluated whether GM(2) ganglioside storage is necessary for neurodegeneration and neuroinflammation by performing ß-hexosaminidase rescue experiments in neurons of HexB(-/-) mice. We developed a novel mouse model, whereby the expression of the human HEXB gene was targeted to neurons of HexB(-/-) mice by the Thy1 promoter. Despite ß-hexosaminidase restoration in neurons was sufficient in rescuing HexB(-/-) mice from GM(2) neuronal storage and neurodegeneration, brain inflammation persisted, including the presence of large numbers of reactive microglia/macrophages due to persisting GM(2) presence in this cell type. In conclusion, our results suggest that neuroinflammation is not sufficient to elicit neurodegeneration as long as neuronal function is restored.

Chronic IL-1ß-mediated neuroinflammation mitigates amyloid pathology in a mouse model of Alzheimer's disease without inducing overt neurodegeneration.

Neuroinflammation is a local tissue response to injurious stimuli in the central nervous system (CNS) and is characterized by glial reactivity, induction of cytokines and chemokines, and vascular permeability. The cytokine interleukin (IL)-1ß is rapidly induced following CNS insult, and is chronically expressed in neurodegenerative disorders such as Alzheimer's disease (AD). We recently developed a novel method of sustained IL-1ß production in the brain to study the link between IL-1ß and AD pathogenesis. Utilizing this model, we have previously demonstrated reduction of plaque size and frequency accompanied by a robust neuroinflammatory response. These observations were limited to a single early time point in the course of AD plaque deposition and did not investigate other neurodegenerative endpoints. To extend these observations to other stages of disease progression and evaluate additional pathologic markers, we investigated the effects of age and duration of IL-1ß overexpression in the APPswe/PS-1dE9 AD model on a congenic C57BL/6 background. We now report that IL1ß overexpression leads to decreased 6E10 immunopositive plaque pathology regardless of age or duration. We also investigated whether IL-1ß overexpression led to neuronal apoptosis or cholinergic axonal degeneration in the context of this AD model. Although we could demonstrate apoptosis of infiltrating inflammatory cells, we found no evidence for IL-1 associated apoptosis of neurons or cholinergic axon degeneration even after 5 months of chronic neuroinflammation. Together, these observations point to a neuroprotective role for IL-1ß in AD neuropathogenesis.

Osteoarthritis accelerates and exacerbates Alzheimer's disease pathology in mice.

BACKGROUND: The purpose of this study was to investigate whether localized peripheral inflammation, such as osteoarthritis, contributes to neuroinflammation and neurodegenerative disease in vivo. METHODS: We employed the inducible Col1-IL1ßXAT mouse model of osteoarthritis, in which induction of osteoarthritis in the knees and temporomandibular joints resulted in astrocyte and microglial activation in the brain, accompanied by upregulation of inflammation-related gene expression. The biological significance of the link between peripheral and brain inflammation was explored in the APP/PS1 mouse model of Alzheimer's disease (AD) whereby osteoarthritis resulted in neuroinflammation as well as exacerbation and acceleration of AD pathology. RESULTS: Induction of osteoarthritis exacerbated and accelerated the development of neuroinflammation, as assessed by glial cell activation and quantification of inflammation-related mRNAs, as well as Aß pathology, assessed by the number and size of amyloid plaques, in the APP/PS1; Col1-IL1ßXAT compound transgenic mouse. CONCLUSION: This work supports a model by which peripheral inflammation triggers the development of neuroinflammation and subsequently the induction of AD pathology. Better understanding of the link between peripheral localized inflammation, whether in the form of osteoarthritis, atherosclerosis or other conditions, and brain inflammation, may prove critical to our understanding of the pathophysiology of disorders such as Alzheimer's, Parkinson's and other neurodegenerative diseases.